Light emitting diodes (LEDs) have been used as backlight for displays and illumination panels for some time, where a large number of low power LEDs are arranged in an array. LEDs are well suited for this purpose for several reasons. They are, for instance, durable structures with a long lifetime, which reduces the maintenance needed. Also, they have a low power consumption and are operated at lower voltages, which reduces costs of operation and risks related to high voltage applications. In relation to this they have an high light output. Prior art techniques include the arrangement of LEDs on printed circuit boards (PCBs). This is, however a costly solution, especially when the LEDs are on a large pitch an larger areas are to be illuminated.